ppc: Zap ICU862 board

This board is the only user of CONFIG_SYS_EEPROM_X40430 , remove
it so the EEPROM command code can be cleansed of the related code
as well.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Tom Rini <trini@ti.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Heiko Schocher <hs@denx.de>